I've asked the question before, and I've had great, success using a piece of solid 18g wire attached to an attic run coax.

If I can get 50' - 100' up there. I'm USUALLY in good shape.

It's also a good idea to have a clause about AM/FM reception in your contracts fine print to release you from responsibility.

We generally use the out of the box antennas, first, then charge minimally for an upgrade. (for which we have already run the wire.)

80% of the time we're doing great with the included antennas.

2% of the time we're glad we have a clause releasing us from responsibility to pull in every station.